Hi, I've been silicon bronze casting sporadically for 20 years, small figurative sculptures of up to 2.5 Kg (5.5 lb US) finished weight. I use ceramic shell, originally ammonia cured, more recently Wexcoat. I use gas-fired ceramic wool furnaces with an incorporated one-lift crucible handling system which makes pouring quicker, easier and safer. For larger pieces I've used cores built up from fire-cement, which remain within, I'd particularly like to know what other people do for cores, I'm suspicious of leaving plaster inside bronze. I have a small MIG-welder for repair work, my skills are minimal. Anyone out there with similar inclinations? Mike.
I agree handling the crucible only once is a big plus. If you decide to do some aluminum casting, and use a metal crucible, this was my solution. http://forums.thehomefoundry.org/index.php?threads/small-aluminum-propane-furnace.1955/#post-48355
Hi Mike There are a hand full of us here that do art type bronzes. Im sure you will find them after a few weeks. I have used cores out of plaster a couple of times. I make sure there are access points that allow me to remove it all with a drill or simple sandblaster. Mostly I allow the ceramic shell to flow inside the sculpture to form the core. and weld the holes closed afterwards. Sometimes I cant access all the shell to remove it so I just leave it in place. It is so tightly adhered to the inside that it isnt going to break free and its quite hard so it doesnt crumble away either. Initially I thought it wouldnt have the ring of a bronze sculpture thinking the shell would dull the sound, but that doesnt seem to be the case. At least not that I can notice. We would love to see some pics of your work if you have any. Start a new thread for them if you can.
hi mike i am doing similar thing making sculpture with shell casting. Ceramic wool kilns and foundry pouring bronze. On a project now and i could really do with a few tips on improving my sprueing bit of a cmoplex project. If your willing i can send some pictures for you to cast your experienced eye over. Thanks for your considerations Tom
Hi Tom, I'm afraid my eye isn't that experienced, I'm almost totally self-taught and each piece is an experiment, but I am very happy to see what you are doing. Sadly I haven't taken many pics of spruing and often I don't remember what I did in that respect. I have found that you don't need that much, apart from things like appendages which would not be self-venting by virtue of their orientation, the porosity of the shell seems to take care of quite a bit. Or I've just been lucky. I've shown one piece (I hope) as an illustration. This is 10" tall, has a core of fire-cement on a stainless wire armature. It was cast upright with the feed at the back between the shoulders, and had only one true vent, from the top of the head. There were 2 connections from the wrists to the respective thighs, these were not vents or feeds, but to stabilise the arms while shelling, I guessed that the arms would fill naturally. The scythe was cast separately, with a substantial main gate with multiple feeds from it. No venting, as I remember. I always feed into the fattest part, orient the piece so that as much of the void as possible will fill by direct flow, and only vent where there is a significant volume of air which would be trapped. I don't know if this is usual practice, anyone out there with better info? Anyway, happy to exchange ideas, I've not been casting for a while and need to get going again. Mike View attachment 23514 View attachment 23516
thanks very much for your time and consideration. its a pleasure to see your syth guy, how did you model the work in wax or clay and did you make a mold too? had a bit of a trouble getting my foundry to fire hot enough over last few days until with a wee chat with a friend to confirm it i had been freezing my gas so it was loosing preasure and failing to heat. thankfully after putting on a big full lpg tank it fired 5 kg bronze to 1180 in 32 min. so chuffed and having heated my shell to 980 it poored fine the vent even filling jut about 9mm lower than the cup level, chuffed. but i think i will go for direct fill from the top of the piece and just vent the air traps as you suggest. do you use a bit of glass fiber strand to reinforce your shell at all? thanks again tom ps will see if i can work out how to put up pictures onto a seperate feed/thread can call it work in progress.
Hi Tom, I'm afraid my eye isn't that experienced, I'm almost totally self-taught and each piece is an experiment, but I am very happy to see what you are doing. Sadly I haven't taken many pics of spruing and often I don't remember what I did in that respect. I have found that you don't need that much, apart from things like appendages which would not be self-venting by virtue of their orientation, the porosity of the shell seems to take care of quite a bit. Or I've just been lucky. I've shown one piece (I hope) as an illustration. This is 10" tall, has a core of fire-cement on a stainless wire armature. It was cast upright with the feed at the back between the shoulders, and had only one true vent, from the top of the head. There were 2 connections from the wrists to the respective thighs, these were not vents or feeds, but to stabilise the arms while shelling, I guessed that the arms would fill naturally. The scythe was cast separately, with a substantial main gate with multiple feeds from it. No venting, as I remember. I always feed into the fattest part, orient the piece so that as much of the void as possible will fill by direct flow, and only vent where there is a significant volume of air which would be trapped. I don't know if this is usual practice, anyone out there with better info? Anyway, happy to exchange ideas, I've not been casting for a while and need to get going again. Mike View attachment 23514 View attachment 23516
Hi Tom, straight lost wax, no moulds. I tried using glass-fibre reinforcement, didn't get on with it. I find that most of my shells crack a bit on burn-out, but I repair the warm shell by a further application of slurry to cement the cracks, thick enough not to penetrate right through the cracks to the void (where it would cause casting defects). Seems to have worked so far. One of the reasons I joined was to get some answers myself! What were you casting?
